Antarctica is changing, and wildlife and weeds could be on the way

2022-12-01

Only a tiny portion of Antarctica — less than 1 per cent — is permanently ice-free.

Yet that’s where the bulk of its unique plants, mosses, lichens, algae, invertebrates and animals manage to survive.

But that’s all changing. Between now and the end of the century, thousands of square kilometres of permanently ice-free habitat is going to open up on the continent, even under moderate climate change.

In general, growing seasons will get longer, more precipitation will fall as rain, more fresh meltwater will be released, average temperatures will become milder, and extreme weather events, like elsewhere, are likely to become more intense.

Put that all together, and what you get is a transformation of parts of the world’s most untouched environment.

So researchers have painted a picture of what that is going to look like, publishing their analysis in Global Change Biology.

March of the penguins?

“Some penguin species are going to win, but others are going to lose,” said co-author Justine Shaw from Securing Antarctica’s Environmental Future, at the Queensland University of Technology.

Gentoo penguins are already advancing into new habitats as ice retreats in Western Antarctica, as are Adelie penguins on Beaufort Island and king penguins on sub-Antarctic South Georgia, the analysis stated.

This is a really important point.

Antarctic soils buried under ice for millennia are typically nutrient-poor and incapable of supporting much life.

But penguin poo, or “guano”, is packed with nutrients like nitrogen and phosphorous, as well as trace metals.

In that way, penguins act as ecosystem engineers — as they advance into freshly uncovered habitats, they help ready the soil for things like plants, lichen and mosses to move in.

So much so that vegetation growth on newly exposed soil can betray the location of ancient penguin colonies, which existed during previous periods of warming.

Scientists are able to use soil analysis to confirm those locations.

“You look and say, ‘why is there a big moss bed here?’,” Dr Shaw said.

“Ice can melt and expose an ancient penguin colony, where you have nutrients locked away in that soil.”

But it’s not all good news for penguins. Some like the emperor penguin depend on sea ice for breeding and feeding.

“The emperor penguin is looking like it’s really not going to cope well with climate change. It doesn’t occur anywhere else in the world.”

Will we see trees on Antarctica?

There are currently only two species of flowering plant native to Antarctica — Antarctic hair grass and Antarctic pearlwort.

Both are thought to have colonised Antarctica multiple times over tens of thousands of years, via wind and animals from South America.

But if penguins and shorebirds are priming more ice-free areas for vegetation, could we see trees move onto the continent?

“Certainly not in our lifetime. We don’t have trees on the sub-Antarctic islands yet,” Dr Shaw said.

It’s not just the harsh conditions keeping trees at bay either.

“The Southern Ocean is a pretty massive barrier,” she said. Seeds would have to remain viable after crossing that vast body of saltwater in order to establish themselves in Antarctica.

But some non-native plants and invertebrates have managed to make it. So how have they done it?

“Where we’ve already had weeds and invasive species in Antarctica is where people have been,” Dr Shaw said.

In fact, many non-native species have hitchhiked with humans to Antarctica, and it’s thought that 11 invertebrates and plants have managed to establish themselves in the past.

Again though, because of the harsh conditions, they haven’t managed to spread far and eradication has been generally successful.

But as more ice-free areas expand and the distance between them shrinks, what we’re likely to see is increased connectivity — the ability for species to move between and colonise new habitats.

And while that means some native species will spread out, it also increases the risk of pests getting a foothold — especially as human traffic rises.

Rats have decimated shorebirds on sub-Antarctic islands

A 2012 study found that visitors to Antarctica, including researchers, carried on average more than nine seeds per person attached to their clothing.

And mammals have managed to hitchhike their way to sub-Antarctic islands.

It’s not impossible that something like rats could, in the future, wreak havoc in Antarctica.

“It’s a long way off,” Dr Shaw said.

“[But] when we look at the sub-Antarctic islands — Macquarie Island, Heard Island — we’ve seen invasive mammals on those islands and we’ve seen the damage they do.

“They’re a great testament to why we should have tight security in Antarctica.”

Even without the introduction of pests to the white continent, glaciologist Felicity McCormack from Monash University said retreating ice could allow some native species to outcompete others.

“We could see that some species potentially benefit from changes in ice-free areas, but that could lead to an overall decrease in biodiversity,” said Dr McCormack, who wasn’t involved in the analysis.

“We don’t tend to associate biodiversity with Antarctica, but it’s crucial just like everywhere else on Earth.

“I think there’s a real imperative to do what we can to prevent further warming now.”

The guiding principle, according to Dr Shaw, is that we should be trying to prevent extinctions.

“This is the last true wilderness in the world. If we can’t stop species going extinct in Antarctica, that’s pretty depressing.”

ABC News, 1 December 2022
; https://abc.net.au